Nesses



Patented Jm'zv, 1931 1,790,552

UNITEDSTATESD' PATENT- OFFVICE aucusrus 1'. mm, or onarranooea, TENNESSEE, Assrenon. 'ro mnnnrmrrn nun conronarron, or cum-mucosa, rnnmsnn, A conromvrron or m- NESSEE ALLOY ron mnnrao'ruan or cas'r mon No Drawing, Application filed- Angust 29, 1988. Serial 1Io. 802,389.

The present invention relates to the treatment of metals, and, .more particularly, to the treatment of molten metal in the manufacture of castings.

5 An object of the invention is to provide a process for the manufacture of castings of special strength and uniformity, such as will insure the quality sought in the finished castm eretofore, when deemed essential, it has been the practice in the manufacture of grey iron castings to add to the molten metal a suitable agent in order to obtain the carbon in the desired forms.

In the breaking down of the iron carbide in the metal during solidification, ferro-silicon generally has been used as a graphitizing agent in order to provide the proper ratio of combined and graphitic carbon in the casting, and in a treatment of molten metal such as would upon solidification produce a casting white in fracture, into metal for castings the fracture of which would be grey, the use of the silicide substantially free from iron is suggested in my Patent 1,499,068, granted June 24th, 1924.

My investigations have disclosed that the character of grey castings may be materially improved by the treatment of molten metal for making castings which would be gray but which ordinarily would have rather limited mechanical properties, through the introduction in the molten metal of a silicide substantially free from iron. It has been found that a silicide of an alkaline earth metal,'such as calcium or magnesium, or other alkaline earth metal, will materially improve the casting, even though it contains an amount of graphitic carbon that was not precipitated by the silicide referred to, and would have been grey in fracture without the introduction of the silicide.

The introduction of such a silicide, even in molten metal which, when cast, ordinarily would be grey in character, is readily soluble and workable, and acts to precipitate additional carbon in spite of which the tensile and transverse strength will be materially increased. It has been found that the silicide 50 produces this effect in molten iron adapted to produce a casting containing approximately 3% of combined carbon, and even in iron containing less than 1% of combined carbon.

By the statement that the silicide is substantially free from iron, is meant that the iron content of the treating agent or alloy is relatively inconsiderable.

I have also found that in the production of castings, the silicide agent may be accompanied to advantage by a second alkaline earth metal, such as magnesium, strontium. barium, etc. For example, an alloy agent of calcium, silicon and an inconsiderable amount of iron may also include to advantage either magnesium or strontium or barium, etc. m

The agents described above, when used separately or combined as alloys, have been found to be of increased or intensified value if accompanied by nickel, or aluminum, or chromium, or titanium or vanadium. In some instances, more than one of these elements may be employed to advantage; for example both nickel and chromium. The addition of this second element, especially chromium has been found to increase the capacity of the metal to resist high pressures and temperatures. Also it increases the resistance to acids and acidic oil vapors.

The following alloys are given as examples pf ones that have been found to be satisfacory:

Ewample 4 Per cent Calcium Magnesium 9 Silicon 36 Example 5 Per cent Silicon Nickel 5 Magnesium 9 Calcium 35 Example 6 Per cent Silicon 53 to 60 Calcium 32. 60 to 35 Nickel 2. 60 Chromium 1 Iron 3 These agents may be introduced into the molten metal, in any suitable manner, either in combination, i. e., as alloys, or separately. ordinarily the alloy 01' separate elements are reduced to relatively small particles, although the alloy may be used in brick or briquette form, and a few ounces of the same used to a small percentage of the metal treated. The agents may be added in the spout as the molten metal runs from the furnace, or thrown into the stream of metal where it enters the ladle from the spout, or else added to the metal in the furnace.

Although the percentages given in the foregoing examples may be varied considerably, it is to be understood that where reference is made in the specification and claims tothe use of a silicide, such as calcium or magnesium silicide, I mean an amount of the same suflicient to produce an appreciable graphitizing efiect. Since the molten iron will Vary in. its characteristics, the amount of silicide needed, in particular instances, will be governed accordingly, the silicide being used, of course, in sulficient amounts to produce the desired graphitizing efi'ect.

By molten white iron', I mean such molten iron as will produce castings substantially free from graphitic carbon. By white iron I mean such castings as are substantially free from graphitic carbon. By gray molten iron I mean such molten iron as will produce castings in which more or less amount up to 5%, and a second alkaline metal of the calcium-magnesium group in a percentage somewhat less than one-half the percentage of the first alkaline metal.

2. An alloy for the use in the treatment of molten iron for making cast iron containing the following in substantially the propor- 1 tions specified: silicon, 53% to 60%; calcium, 32.60% to 35%; nickel, 3.60%; iron, 2.60%.

3. An alloy for the use in the treatment of molten iron for making cast iron containing the following in substantially the roportions specified: calcium, 35% magnesium, 9%; silicon, 56%. a

4. An alloy for the use in the treatment of molten iron for making cast iron containing the following in substantially the .proportions specified: silicon, 51%; nickel, 5%; magnesium, 9%; calcium, 35%.

In testimony whereof I have hereunto set my hand.

AUGUSTUS F. MEEHAN. 

